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view spandsp-0.0.3/spandsp-0.0.3/src/spandsp/v27ter_rx.h @ 5:f762bf195c4b
import spandsp-0.0.3
author | Peter Meerwald <pmeerw@cosy.sbg.ac.at> |
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date | Fri, 25 Jun 2010 16:00:21 +0200 |
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/* * SpanDSP - a series of DSP components for telephony * * v27ter_rx.h - ITU V.27ter modem receive part * * Written by Steve Underwood <steveu@coppice.org> * * Copyright (C) 2003 Steve Underwood * * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2, as * published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * * $Id: v27ter_rx.h,v 1.34 2006/10/24 13:45:28 steveu Exp $ */ /*! \file */ #if !defined(_V27TER_RX_H_) #define _V27TER_RX_H_ /*! \page v27ter_rx_page The V.27ter receiver \section v27ter_rx_page_sec_1 What does it do? The V.27ter receiver implements the receive side of a V.27ter modem. This can operate at data rates of 4800 and 2400 bits/s. The audio input is a stream of 16 bit samples, at 8000 samples/second. The transmit and receive side of V.27ter modems operate independantly. V.27ter is mostly used for FAX transmission, where it provides the standard 4800 bits/s rate (the 2400 bits/s mode is not used for FAX). \section v27ter_rx_page_sec_2 How does it work? V.27ter defines two modes of operation. One uses 8-PSK at 1600 baud, giving 4800bps. The other uses 4-PSK at 1200 baud, giving 2400bps. A training sequence is specified at the start of transmission, which makes the design of a V.27ter receiver relatively straightforward. */ /* Target length for the equalizer is about 43 taps for 4800bps and 32 taps for 2400bps to deal with the worst stuff in V.56bis. */ #define V27TER_EQUALIZER_PRE_LEN 15 /* this much before the real event */ #define V27TER_EQUALIZER_POST_LEN 15 /* this much after the real event */ #define V27TER_EQUALIZER_MASK 63 /* one less than a power of 2 >= (V27TER_EQUALIZER_PRE_LEN + 1 + V27TER_EQUALIZER_POST_LEN) */ #define V27TER_RX_4800_FILTER_STEPS 27 #define V27TER_RX_2400_FILTER_STEPS 27 #if V27TER_RX_4800_FILTER_STEPS > V27TER_RX_2400_FILTER_STEPS #define V27TER_RX_FILTER_STEPS V27TER_RX_4800_FILTER_STEPS #else #define V27TER_RX_FILTER_STEPS V27TER_RX_2400_FILTER_STEPS #endif /*! V.27ter modem receive side descriptor. This defines the working state for a single instance of a V.27ter modem receiver. */ typedef struct { /*! \brief The bit rate of the modem. Valid values are 2400 and 4800. */ int bit_rate; /*! \brief The callback function used to put each bit received. */ put_bit_func_t put_bit; /*! \brief A user specified opaque pointer passed to the put_bit routine. */ void *user_data; /*! \brief A callback function which may be enabled to report every symbol's constellation position. */ qam_report_handler_t *qam_report; /*! \brief A user specified opaque pointer passed to the qam_report callback routine. */ void *qam_user_data; /*! \brief The route raised cosine (RRC) pulse shaping filter buffer. */ float rrc_filter[2*V27TER_RX_FILTER_STEPS]; /*! \brief Current offset into the RRC pulse shaping filter buffer. */ int rrc_filter_step; /*! \brief The register for the training and data scrambler. */ unsigned int scramble_reg; /*! \brief A counter for the number of consecutive bits of repeating pattern through the scrambler. */ int scrambler_pattern_count; int in_training; int training_bc; int training_count; float training_error; int carrier_present; int16_t last_sample; /*! \brief TRUE if the previous trained values are to be reused. */ int old_train; /*! \brief The current phase of the carrier (i.e. the DDS parameter). */ uint32_t carrier_phase; /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */ int32_t carrier_phase_rate; /*! \brief The carrier update rate saved for reuse when using short training. */ int32_t carrier_phase_rate_save; float carrier_track_p; float carrier_track_i; power_meter_t power; int32_t carrier_on_power; int32_t carrier_off_power; float agc_scaling; float agc_scaling_save; int constellation_state; float eq_delta; /*! \brief The adaptive equalizer coefficients */ complexf_t eq_coeff[V27TER_EQUALIZER_PRE_LEN + 1 + V27TER_EQUALIZER_POST_LEN]; complexf_t eq_coeff_save[V27TER_EQUALIZER_PRE_LEN + 1 + V27TER_EQUALIZER_POST_LEN]; complexf_t eq_buf[V27TER_EQUALIZER_MASK + 1]; /*! \brief Current offset into equalizer buffer. */ int eq_step; int eq_put_step; int eq_skip; /*! \brief Integration variable for damping the Gardner algorithm tests. */ int gardner_integrate; /*! \brief Current step size of Gardner algorithm integration. */ int gardner_step; /*! \brief The total symbol timing correction since the carrier came up. This is only for performance analysis purposes. */ int total_baud_timing_correction; /*! \brief The current fractional phase of the baud timing. */ int baud_phase; /*! \brief Starting phase angles for the coarse carrier aquisition step. */ int32_t start_angles[2]; /*! \brief History list of phase angles for the coarse carrier aquisition step. */ int32_t angles[16]; /*! \brief Error and flow logging control */ logging_state_t logging; } v27ter_rx_state_t; #ifdef __cplusplus extern "C" { #endif /*! Initialise a V.27ter modem receive context. \brief Initialise a V.27ter modem receive context. \param s The modem context. \param rate The bit rate of the modem. Valid values are 2400 and 4800. \param put_bit The callback routine used to put the received data. \param user_data An opaque pointer passed to the put_bit routine. \return A pointer to the modem context, or NULL if there was a problem. */ v27ter_rx_state_t *v27ter_rx_init(v27ter_rx_state_t *s, int rate, put_bit_func_t put_bit, void *user_data); /*! Reinitialise an existing V.27ter modem receive context. \brief Reinitialise an existing V.27ter modem receive context. \param s The modem context. \param rate The bit rate of the modem. Valid values are 2400 and 4800. \param old_train TRUE if a previous trained values are to be reused. \return 0 for OK, -1 for bad parameter */ int v27ter_rx_restart(v27ter_rx_state_t *s, int rate, int old_train); /*! Release a V.27ter modem receive context. \brief Release a V.27ter modem receive context. \param s The modem context. \return 0 for OK */ int v27ter_rx_release(v27ter_rx_state_t *s); /*! Change the put_bit function associated with a V.27ter modem receive context. \brief Change the put_bit function associated with a V.27ter modem receive context. \param s The modem context. \param put_bit The callback routine used to handle received bits. \param user_data An opaque pointer. */ void v27ter_rx_set_put_bit(v27ter_rx_state_t *s, put_bit_func_t put_bit, void *user_data); /*! Process a block of received V.27ter modem audio samples. \brief Process a block of received V.27ter modem audio samples. \param s The modem context. \param amp The audio sample buffer. \param len The number of samples in the buffer. \return The number of samples unprocessed. */ int v27ter_rx(v27ter_rx_state_t *s, const int16_t amp[], int len); /*! Get a snapshot of the current equalizer coefficients. \brief Get a snapshot of the current equalizer coefficients. \param coeffs The vector of complex coefficients. \return The number of coefficients in the vector. */ int v27ter_rx_equalizer_state(v27ter_rx_state_t *s, complexf_t **coeffs); /*! Get the current received carrier frequency. \param s The modem context. \return The frequency, in Hertz. */ float v27ter_rx_carrier_frequency(v27ter_rx_state_t *s); /*! Get the current symbol timing correction since startup. \param s The modem context. \return The correction. */ float v27ter_rx_symbol_timing_correction(v27ter_rx_state_t *s); /*! Get a current received signal power. \param s The modem context. \return The signal power, in dBm0. */ float v27ter_rx_signal_power(v27ter_rx_state_t *s); /*! Set the power level at which the carrier detection will cut in \param s The modem context. \param cutoff The signal cutoff power, in dBm0. */ void v27ter_rx_signal_cutoff(v27ter_rx_state_t *s, float cutoff); /*! Set a handler routine to process QAM status reports \param s The modem context. \param handler The handler routine. \param user_data An opaque pointer passed to the handler routine. */ void v27ter_rx_set_qam_report_handler(v27ter_rx_state_t *s, qam_report_handler_t *handler, void *user_data); #ifdef __cplusplus } #endif #endif /*- End of file ------------------------------------------------------------*/